Fizzer

Fizzer.fs

type FizzBuzzer = int -> string

module FizzBuzzer =
    
    type ValidFizzBuzzer = private ValidFizzBuzzer of FizzBuzzer
    
    let createFizzBuzzer (possibleFizzBuzzer: FizzBuzzer) : Result<ValidFizzBuzzer, string> =
        if possibleFizzBuzzer 3  = "Fizz" then
            Ok (ValidFizzBuzzer possibleFizzBuzzer)
        else
            Error "Cannot create a ValidFizzBuzzer must return 'Fizz' for 3"
    
    let runner (fizzBuzzer:Result<ValidFizzBuzzer, string> ) : string list =
        match fizzBuzzer with
        | Ok (ValidFizzBuzzer fb) ->
            [0 .. 10 ] |> List.map fb
        | Error e -> [e]


        
[<EntryPoint>]
let main args : int =
    let badBuzzer = fun (x :int ) -> "Buzz"
    
    let goodBuzzer =
        fun (x :int ) ->
            match x % 3, x % 5 with
            | 0, 0 -> "FizzBuzz"
            | 0, _ -> "Fizz"
            | _, 0 -> "Buzz"
            | _, _ -> string x
    
    printfn "Running badBuzzer"
    badBuzzer |> FizzBuzzer.createFizzBuzzer |> FizzBuzzer.runner |> List.iter (printfn "%s")
    
    printfn "Running goodBuzzer"
    goodBuzzer |> FizzBuzzer.createFizzBuzzer |> FizzBuzzer.runner |> List.iter (printfn "%s")
   
    0